| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: More stable query plans via more predictable column statistics |
| Date: | 2016-03-09 16:28:14 |
| Message-ID: | 26465.1457540894@sss.pgh.pa.us |
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"Shulgin, Oleksandr" <oleksandr(dot)shulgin(at)zalando(dot)de> writes:
> Yes, I now recall that my actual concern was that sample_cnt may calculate
> to 0 due to the latest condition above, but that also implies track_cnt ==
> 0, and then we have a for loop there which will not run at all due to this,
> so I figured we can avoid calculating avgcount and running the loop
> altogether with that check. I'm not opposed to changing the condition if
> that makes the code easier to understand (or dropping it altogether if
> calculating 0/0 is believed to be harmless anyway).
Avoiding intentional zero divides is good. It might happen to work
conveniently on your machine, but I wouldn't think it's portable.
regards, tom lane
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